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- Thermal and environmental simulation of buildingsPublication . Ramos, João António Esteves; Pitarma, Rui A.; Carvalho, Maria da GraçaThe purpose of most buildings is to provide a comfortable and healthy indoor environment for the occupants. As a result of increasing energy prices in the last decades, much effort has been done to reduce the cost arising from mechanical and natural ventilation of buildings. This often involves lowering the outdoor air intake. At the same time, many new pollution sources have been introduced in the buildings. These issues are important if we take into consideration that today the majority of the people spends more than 90% of their time indoors. In this work will be presented a physical and mathematical models to study the three-dimensional turbulent air flow patterns with thermal buoyant effects, the heat transfer, including radiation between walls, the gas contaminant trasnport and the most air transport into mechanical or natural ventilated spaces. the calculations made use of a numerical procedure, which solves the three-dimensional equations for the conservation of mass, momentum, thermal energy and air contaminant transport. The turbulence is modelled by the k-e model and thermal radiation by the discrete transfer method. To validate the mathematical model, the predictions results were compared with experimental data for two different scales - full scale office room and 1/4 laboratory scale model. A physical modelling technique, based on dimensional analysis, was used to derive the physical properties of the laboratory model, designed to provide similarity with the room. The simulation of the air contaminant distribution, the thermal and the air flow patterns in an office natural ventilated room (prototype and model) was performed.
- Dynamic analysis of a refrigerated roomPublication . Carvalho, Maria da Graça; Pitarma, Rui A.; Pereira, Filipe D.; Ramos, João António EstevesThe prediction of velocity and temperature distributions in a refrigerated room generally requires the simultaneous three-dimensional solution of the equations governing the flow pattern (Navier-stokes equations for buoyant flows) and the energy equation. This paper presents numerical predictions and experimental validation of the three-dimensional turbulent flow inside two different three-dimensional refrigeration chambers with forced convection. The refrigerated rooms are a 26 m3 living produce storage room and a 10 m3 yogurt truck refrigerated chamber. Agreement between measured and predicted values was very satisfactory for engineering purposes. The model is very useful in chamber's design since an important tool to predict food storage in order to allow energy savings.
- Three-dimensional natural convection in rooms connected to the outside through large openingsPublication . Ramos, João António Esteves; Martinho, Nuno A. G.; Pitarma, Rui A.; Carvalho, Maria da GraçaThe growing interest in the study of natural convection in geometrically complex enclosures with restricted communication has been stimulated by applications involving energy-efficient passive-solar buildings, natural convection cooling of electronic equipment and room heating and ventilation. Airflow through doorways, windows and other large openings are significant ways in which air, pollutants and thermal energy are transferred from one zone of a building to another or to outside. The present paper describes a numerical method for analysing three-dimensional natural convection in rooms connected to the outside through large openings. The calculations made use of a Computational Fluid Dynamics (CDF) procedure taking into account the effects of buoyancy, heat sources, thermal radiation heat transfer and air flow turbulence. The CDF predictions agree with the experimentally observed features of the flow field, including the vertical air temperature stratification, with a reasonable degree of accuracy.
- The role of computational fluid dynamics in the building energy and environmental analysisPublication . Carvalho, Maria da Graça; Ramos, João António EstevesThe goal of this paper is to introduce a Computational Fluid Dynamics model to study the steady three-dimensional turbulent airflow pattern, with thermal buoyant effects, the heat transfer, the gas contaminant transport and the moist air transport into mechanical or natural ventilated spaces, with furniture and people. The calculations made use of a numerical procedure with solves the three-dimensional steady state equations for the conservation of mass, momentum, thermal energy and air contaminant transport, tanking account of the effects of buoyancy and airflow turbulence. In order to demonstrate its applicability, the code has been used to predict the thermal, the airflow pattern and the environment in an office ventilated room. Based on this predictions and on thermal comfort models it was possible to evaluate the thermal comfort.
- O papel da modelação matemática na optimização da climatização de edifíciosPublication . Ramos, João António Esteves; Pitarma, Rui A.; Martinho, Nuno A. G.; Carvalho, Maria da GraçaA crescente necessidade da utilização de meios de cálculo que permitam a previsão e a visualização das características dos escoamentos do ar, da distribuição da temperatura, da distribuição da humidade do ar e do transporte de contaminantes, em espaços de edifícios ventilados, tem incentivado a investigação na modelação física e matemática desses fenómenos, nessas geometrias complexas. Nesta comunicação, apresenta-se uma "ferramenta" de cálculo que permite modelar os fenómenos tridimensionais associados à circulação turbulenta do ar, à transmissão de calor e à transmissão do vapor de água no ar (humidade). O modelo de simulação computacional desenvolvido foi validado para a caracterização do ambiente interior em edifícios nas suas variantes termo-higrométricas, qualidade do ar e conforto térmico. Nesta comunicação apresentam-se previsões do campo da velocidade, da temperatura do ar e da concentração de vapor de água numa sala de escritório com obstáculos e com fontes interiores de calor e de água. Este tipo de avaliação é fundamental para, em cada caso, conhecer, de uma forma detalhada, a influência dos vários parâmetros do ambiente interior nos ocupantes dos edifícios, quer do ponto de vista do conforto térmico, quer da qualidade do ar.
- Modelação do conforto térmico em salas climatizadasPublication . Ramos, João António Esteves; Pitarma, Rui A.; Carvalho, Maria da GraçaThe goal of this lecture is to introduce a new tool to predict the three-dimensional turbulent air flow pattern and the heat transfer in ventilated buildings
- Indoor air quality audit in two office buildings in PortugalPublication . Ramos, Joao; Pinto, FernandoThe indoor air quality that a building presents is not always from our knowledge. In fact, we may find ourselves exposed to an indoor air which can be harmful to human health, affecting the quality of life and productivity, which also will have economic repercussions at this level. Given the Portuguese law for energy and indoor air quality (IAQ) certification of large service buildings, the indoor air quality requirements were here presented and, in addition, this paper provides an overview of the current Portuguese IAQ technical procedures to audit existent buildings. It was also intended with this study to evaluate the indoor air quality experienced by the occupants of two office buildings, an old and a recent, with the same activity and occupancy, without air-conditioning systems, where were carried out indoor air quality characterizations and, in particular, have been assessed the CO2 concentration and the typical renewal air exchange rates in different zones of the buildings, as a ventilation effectiveness monitoring. During the building's regular occupancy period, the authors have been done monitoring campaigns, which took place in winter and summer seasons. They have been detected that the values of some parameters under review were non-compliance situations in winter, in contrast with the summer due to the increase of ventilation promoted by the occupants taking advantage of the favourable conditions of the Mediterranean weather. Consequently, the proposed IAQ audit approach may be helpful to characterize indoor air pollutants, to evaluate the ventilation effectiveness and to correlate it with the indoor air quality perception and self-control actions of the occupants.
- Improving occupational health by modelling indoor pollutant distributionPublication . Pitarma, Rui; Lourenço, Miguel; Ramos, JoaoPurpose Indoor environments are characterized by several pollutant sources. Some of these can be sufficiently characterized through the prediction of the airflow and pollutant distribution patterns. The purpose of this study was to simulate, analyze and compare different locations of known pollutant source inside a ventilated room. Design/methodology/approach Computational fluid dynamics modelling approach was used to analyze the prediction of the airflow and pollutant distribution patterns for different locations of known pollutant source inside a ventilated room by mixing ventilation. Findings Distinct areas of poor air quality, perfectly identified by concentration fields, were given. The indoor air quality obtained by the different simulated conditions was analyzed and compared. Research limitations/implications Pollutant concentration was not measured in the validation experiments (qualitative validation based on the velocity fields). Practical implications Once the contaminant concentration fields are calculated based on the source location, the model is very useful to choose the best place to install any pollutant indoor equipment to preserve breathing zones. Originality/value Providing an effective indoor air quality assessment to prevent exposure risk. The results would be useful for making decisions to optimize the design procedure, such as establish the best location to install polluting equipment, occupied areas and their interdependence with ventilation systems. In addition, this tool also helps to choose the best location and correct set point adjustment for the pollutant sensors.
- Efficiency in an Intensive Energy Industrial ConsumerPublication . Galvão, J.; Nabais, A.; Galvão, M.; Candeias, J.; Pereira, Thiago; Ramos, J.Energy efficiency actions were made in a glass production industry such as reduction in the energy consumption that will reduce greenhouse gas emissions. All measures were applied regarding European Union-EU guidelines and legislation.
- The Effect of a Naturally Ventilated Roof on the Thermal Behaviour of a Building under Mediterranean Summer ConditionsPublication . Ramos, João; Aires, LuisWith the increasing cost associated with energy consumption, climate change and the greater awareness of the population to issues related to energy and environmental efficiency, energy conservation in buildings has been encouraged, along with the development of several solutions based on a more sustainable construction. Building cooling is the most challenging issue in the Mediterranean climate. The roof is one of the main elements of the building’s opaque envelope, where the choice of materials and the implementation of appropriate passive technologies determine the thermal performance of a building. The present work aims to assess the impact of natural ventilation of a roof cavity on the thermal environment of a dwelling house under Mediterranean summer conditions. An experimental study was developed in a small-scale prototype of a typical dwelling house, comprising a ceramic tile roof with vented eaves and insulated sub-tile panels according to the construction solution of the Humbelino Monteiro SA company. The thermal performance of this roof solution was assessed under real climatic conditions based on continuous measurements of the air velocity inside the air gap, the temperature of the air and the surface temperature of all roof layers. Weather conditions were also monitored continuously. Connected with the heat transfer mechanisms, the obtained temperature and air velocity profiles data were analysed and discussed.